The Hashemites, officially the House of Hashim, are the royal family of Jordan, which they have ruled since 1921. The family traces its descent to Hashim ibn Abd Manaf, the great-grandfather of the Prophet Muhammad, and ruled the holy city of Mecca for centuries, often as vassals of larger powers.
After allying with the British Empire in World War I and leading the Arab Revolt, Hashemites also held the thrones of the Hejaz (1916 to 1925), Syria (1920) and Iraq (1921 to 1958). Today Jordan, whose official name is the Hashemite Kingdom of Jordan, is the only country they still rule, currently under King Abdullah II.
Source: Hashemites, Wikipedia
Image: Flag of Jordan, public domain, via Wikimedia Commons.